Patent document EP 1 653 075 A2 discloses a fuel filter device comprising a fuel filter and a fuel tank. In the fuel filter, water that accumulates in a water collection chamber of the fuel filter is separated. The water is actively drawn off from the bottom of the water collection chamber via a Venturi nozzle and pumped back into the tank.
U.S. Pat. No. 5,462,658 A discloses a water-separating fuel filter having a housing, on the underside of which a water collection chamber is constructed. A central suction tube running in a longitudinal direction of the filter is arranged in the housing in order to suction a separated water-fuel mixture out from the water collection chamber.
Patent document US 2005/0121374 A1 discloses a fuel filter device having a water-separating fuel filter. Water separated in the fuel filter is passed from the bottom of a water collection chamber of the fuel filter into a second water collection chamber via a discharge, the second water collection chamber being arranged in the fuel tank. In the second water collection chamber, further separation of the water takes place.
Patent document DE 37 40 804 C1 discloses a fuel supply device for an internal combustion engine. The fuel supply device comprises a water-separating fuel filter having a water collection chamber. If the water accumulating in the water collection chamber exceeds a predetermined level, then an alarm is triggered.
In order to be able to continue operating the fuel supply device even when the alarm is ignored, a dip tube projects into the water collection chamber and a part of the water can be returned to the tank from the water collection chamber via the dip tube.
Patent document WO 2006/080875 A1 also discloses leading water back into a tank from a water collection chamber of a fuel filter.
Patent document EP 2 078 845 A1 discloses recirculating water from a water collection chamber of a fuel filter into a fuel tank. The recirculation of the water takes place via a throttle for adjusting the recirculated water rate.
Finally, patent document WO 2010/020489 A1 discloses a fuel filter comprising a first water separator. Water that is separated at the first water separator flows into a water collection chamber of the fuel filter via a discharge. In the water collection chamber, the water is set apart from the residual fuel. At the upper side of the water collection chamber, there is an outlet through which the contents of the water collection chamber are returned to a tank.
The fuel filters known from the prior art have a disadvantage in that due to the arrangement of the outlet in the water collection chamber, predominantly the water content of the separated water-fuel mixture is returned to the tank.